add groupedlayercontrol plugin (#1592)

* add groupedlayercontrol plugin

* docstring

* test for group layer control plugin

* remove ws to pass flake

* fix lint errors on test

* add plugin to __all__ in __init__ file

* dont need to add base layers; parent class LayerControl will render

* dont need to add base layers; parent class LayerControl will render

* example notebook

* ws lint issue

* rework

* Update plugin-GroupedLayerControl.ipynb

Co-authored-by: Chansoo Song <chansoo.song@ag.ny.gov>
Co-authored-by: Chansoo Song <chansoosong@chansoos-air.myfiosgateway.com>
Co-authored-by: Frank <33519926+Conengmo@users.noreply.github.com>

Author: 4 people

.gitignore

@@ -25,3 +25,4 @@ latest_logs/
 folium/_version.py
 .vscode/
 venv/
+.venv